Backfire under loads

[kazoocruiser]

Originally Posted by liftlawssuck

I did a quick compression check and all were 120lbs and above. I haven't done a differential check yet.

Intake is Edelbrock Performer.

Me thinks you might have to go back and put about 2 tablespoons of oil in the spark plug hole of the cylinder you are testing to see what a wet compression test indicates. Assuming that you did your initial test with the throttle open while cranking, 120 psi on a dry test indicates worn out rings, or the possibility of compression gas leaking past a valve. If your readings jump up dramatically with a wet test, it isn't the valves.

The other thing I would suggest is putting a vacuum gauge on a manifold source and using what it tells you to help sort out if you have a hidden problem. Watch the gauge to see whether the numbers jump around, climb, or stay stable.

https://www.motor.com/magazine-summa...-vacuum-gauge/

I didn't see it mentioned in the thread, but do you have any idea how many miles are on the "82 K10 with a 305"?